How Skimmers Work and What to Look For
by: Demi Fortuna
Skimmers take advantage of one of the unique qualities of water, surface tension, to effectively clear ponds of any debris that floats, even if only for a short time. The ‘skin’ on the surface of the pond is actually tougher than you might think. Insects like the water strider and water spider walk on it like we walk across the street, because that skin will support a surprising amount of weight as long as it’s well-distributed. As a sheet, it’s also surprisingly resistant to tearing. If you pull on one side of the sheet, you can actually drag the whole surface across large distances. That’s exactly what a well-designed Skimmer does.
All Skimmers have an opening that allows water in, called a weir, and most have a floating door that keeps tension on the skin of the water by directing most of the ‘pull’ to the surface. A properly designed Skimmer matches the pump to the width of the weir. Too little pump or too wide a weir and the pull won’t be sufficient; too much pump or too narrow a weir and the surface will tear; lots of water will pour into the Skimmer but little debris will make it across the pond. Stay at the middle of the manufacturer’s recommended range for best results.
All Skimmers have some way to collect that debris; how they collect it might be even more important. Look for generously sized nets, mats or pads. The smaller they are, the faster they clog, and a clogged mat or pad might keep water from getting to the pump, leading to overheating and potential failure. The best Skimmers have ways to capture debris without starving pumps of water, like brushes that part to let water through even when full of debris, instead of pads that seal off water when neglected too long.
The Skimmer houses and protects the pump, so you’ll want one that’s designed for easy pump connection and removal, and that’s easily cleaned when needed. Finally, since the Skimmer is usually attached to a hole in the liner, the methods and hardware of that attachment must be of the highest quality. Look for stainless steel hardware, not plastic or aluminum, that clamps the liner to the face of the Skimmer securely